As is known, there are today available intracortical-detection systems, also known as recording or micro-recording systems. In particular, systems are known that resort to electrophysiological techniques based upon the use of miniaturized electrodes (micro-electrodes) in order to perform extracellular recordings in vivo. In practice, said systems make direct measurements of electrical quantities indicating the activity of groups of neurons, and consequently enable determination of information regarding the state of health of cerebral cortical portions.
Purely by way of example, in the case of patients affected by low-degree gliomas, current recording systems enable determination with high precision of the boundaries between normal cerebral tissue and pathological cerebral tissue. Consequently, the recording systems are finding increasingly wider use alongside diagnostic systems of a more traditional type.
By way of example, diagnostic systems of a traditional type comprise diagnostic systems that envisage determination of cerebral images on the basis of local measurements of the blood flow, such as for example positron-emission tomography (PET) and functional magnetic resonance imaging (fMRI), or else diagnostic systems that resort to electrophysiological techniques of measurement of the electrical activity of a very numerous neuronal population, such as for example electroencephalography (EEG), electrocorticography (ECoG) and magnetoencephalography (MEG). In general, said diagnostic systems do not present particularly fine spatial and temporal resolutions.
Amongst intracortical-detection systems, there is known the system illustrated in FIG. 1, referred to hereinafter as detection system 1.
In detail, the detection system 1 comprises an intracortical-detection device 2, known also as headstage and referred to hereinafter as detection device 2.
The detection device 2 comprises a first body 3 and a second body 4, arranged in contact with one another, as well as an array of electrodes 6, each of which is designed to contact a corresponding group of neurons in order to enable sensing of the corresponding electrical activity, as described hereinafter. For simplicity of illustration, in FIG. 1 the second body 4 is represented dashed.
The detection device 2 further comprises a first electric motor 8 and a second electric motor 10, as well as an electronic card 11, the latter being housed within the first body 3 and being electrically connected both to the first electric motor 8 and to the second electric motor 10 in order to govern operation thereof. The electronic card 11 is moreover electrically connected to the array of electrodes 6.
In turn, the electronic card 11 is electrically connectable to the outside world. In fact, the detection system 1 further comprises a control station P, which, in use, is connected to the electronic card 11, so that a user can govern, through the control station P, the electronic card 11 itself.
Typically, the connection between the electronic card 11 and the control station P is made by interposition of a peripheral electronic unit 12, which can include, among other things, a field programmable gate array (FPGA). The control of the first and second electric motors 8 and 10 by the user is hence mediated by the electronic card 11 and by the peripheral electronic unit 12.
The first electric motor 8 is a piezoelectric motor of the so-called “stick-and-slip” type, is housed within the first body 3, with respect to which it is fixed, and is coupled to the array of electrodes 6. Moreover, the first electric motor 8 is designed for moving the array of electrodes 6 parallel to a first direction x, in both senses, with a precision of 1 μm. In particular, the array of electrodes 6 is mobile along a longitudinal axis L of the detection device 2, parallel to the first direction x.
In detail, the array of electrodes 6 is constrained to a supporting structure 13, which is operatively coupled to the first electric motor 8 and is mobile under the action of the first electric motor 8, along the longitudinal axis L. Moreover, a portion of the first body 3 defines a contact element 14 having the shape, to a first approximation, of a hollow parallelepiped. The contact element 14 hence defines a cavity 15, inside which the supporting structure 13 and, consequently, the array of electrodes 6, can slide. The amount of this sliding can be set by the user through the control station P. Moreover, the position of the array of electrodes 6 is monitored electronically by means of an infrared marker and a three-dimensional optical tracking system (not illustrated).
As regards the second electric motor 10, it is in part housed within the first body 3, and in part within the second body 4. In particular, the second electric motor 10 is fixed with respect to the first body 3. Moreover, the second electric motor 10 is coupled to a crank 16 and is designed to move this crank 16 with circular motion.
More precisely, the crank 16 is made, for example, of aluminium, and has an elongated shape along a crank axis H, which joins a first end and a second end of the crank 16. In addition, the first end of the crank 16 is constrained to the second electric motor 10.
In practice, the second electric motor 10 is designed to cause the crank 16 to rotate about an axis of rotation R parallel to a second direction y, perpendicular to the crank axis H and to the first direction x.
Even more in particular, the electronic card 11 is able to govern the second electric motor 10 so that the crank 16 assumes any position within a pre-set range; this pre-set range is delimited by two extreme positions, which define an angle for example of ±30°, the angle 0° corresponding to the case where the crank axis H is perpendicular to the first direction x. The user hence cannot impose that the second electric motor 10 causes the crank 16 to rotate outside the pre-set range. This constraint is obtained, for example, by means of appropriate mechanical end-of-travel blocks (not illustrated).
The detection device 2 further comprises a groove 20, fixed with respect to the second body 4 and having an elongated shape, this groove 20 being parallel to a third direction z, perpendicular to the first direction x and the second direction y. Moreover, the detection device 2 comprises a guide 22, a slide 24, and a pin 26.
In detail, the pin 26 is fixed with respect to the crank 16. In particular, the pin 26 is constrained to the second end of the crank 16 and can hence rotate about the axis of rotation R under the action of the second electric motor 10. Moreover, the pin 26 co-operates with the groove 20; i.e., it is mechanically coupled thereto so as to exert a force on the walls of the groove 20 during its own movement about the axis of rotation R.
The guide 22 has an elongated shape and extends parallel to the first direction x. Moreover, the guide 22 is fixed with respect to the first body 3.
The slide 24 is housed within the guide 22. Moreover, the slide 24 can only translate linearly with respect to the guide 22, parallel to the first direction x. For this reason, between the guide 22 and the slide 24 there can be set a bearing (not illustrated).
The slide 24 is moreover fixed with respect to the second body 4, and hence is fixed also with respect to the groove 20. Consequently, following upon rotation, under the action of the second electric motor 10, of the crank 16, and hence of the pin 26, the first and second bodies 3, 4 translate linearly with respect to one another, parallel to the first direction x.
Operatively, the detection device 2 can find advantageous use in the course of a craniotomy, i.e., in the course of a surgical operation in which a portion of the brain of a patient is rendered surgically accessible to the outside world.
In these conditions, it is in fact possible to constrain the second body 4 to the skull of the patient by means of an appropriate mechanical arm (not illustrated) fixed with respect to the second body 4. In particular, the second body 4 is rendered fixed with respect to the skull of the patient, or to a support fixed with respect to the skull (for example, a structure fixed with respect to the operating table), in such a way that the contact element 14 contacts the brain of the patient, as well as in such a way that the first body 3 can move only in a direction parallel to the longitudinal axis L of the detection device 2.
Even more in particular, the contact element 14 defines a surface 30 having the shape of a hollow rectangle, which, in use, is traversed by the array of electrodes 6 and by the supporting structure 13. Moreover, the detection device 2 is constrained to the skull of the patient so that the surface 30 contacts a first portion of the cerebral region.
Next, it is possible to govern the first electric motor 8 so that the array of electrodes 6 translates until it comes into contact with a second portion of the cerebral region, surrounded by the first portion of cerebral region. Through the array of electrodes 6, the electronic card 11 can then acquire electrical signals emitted by the neurons, process them, and make them available to external electronic equipment. Possibly, processing of the electrical signals emitted by the neurons and acquired by the electrodes can be entrusted to the peripheral electronic unit 12.
In greater detail, during a craniotomy there occurs a continuous pulsation of the cerebral tissue due to the variation of the blood pressure caused by the heartbeat, which pumps the blood in an almost periodic way. Moreover, following upon the craniotomy, a sort of bulging of the brain is commonly found to occur.
Both pulsation of the cerebral tissue and bulging of the brain can lead to a deterioration of the quality of the electrical signals acquired by the electronic card 11. In particular, both pulsation of the cerebral tissue and bulging of the brain can modify the electrical signals acquired by the electronic card 11 through the array of electrodes 6, manifesting itself, from an electrical standpoint, in the form of electrical noise.
In order to preserve the quality of the electrical signals acquired by the electronic card 11, ensuring a contact with the outer surface of the brain and hence a spatial reference with respect to this surface, it is known to apply a static pressure in the first portion of cerebral region. In detail, this static pressure is exerted by means of the detection device 2 and in particular by means of the surface 30 of the contact element 14.
In greater detail, it is known to govern, by means of the control station P, the second electric motor 10 so that the first body 3 will translate with respect to the second body 4, the latter, as has been said, being constrained to the skull of the patient. In this way, the static pressure exerted by the surface 30 tends to counteract the bulging of the cerebral tissue.
In practice, typically it is the surgeon who governs, on the basis of his own experience, the motion of the surface 30, and then varies the pressure exerted thereby, without, however, having any information of a quantitative nature regarding the amount of pressure exerted by the cerebral tissue on the surface 30.
Consequently, typically the static pressure exerted by the surface 30 is lower or higher than an optimal pressure. In other words, typically the pressure exerted by the surface 30 is insufficient, or else is so high as to involve the risk that temporary ischaemias of the cerebral tissue might occur, i.e., dangerous interruptions of the bloodflow in the first portion of cerebral region.